Stabilising developed photographic images

ABSTRACT

Exposed and developed pnotographic silver images can be stabilized by treating the layer containing the exposed image with a compound which reacts with the silver halide in the unexposed and undeveloped areas of the layer to form a lightinsensitive reaction product. Fading of the silver images thus produced is prevented by performing the development in the presence of mercapto substituted heterocyclic compounds.

States ate [191 Berthold et al.

[ 1 Fe1n.27,1973

[ STABILISING DEVELOPED PHOTOGRAPHIC IMAGES [73] Assignee: Agia-Gevaert Aktiengesellschaft,

Leverkusen, Germany 22 Filed: April 1,1970

21 Appl. No.: 24,868

[30] Foreign Application Priority Data April 15, 1969 Germany ..P l9 19 045.5

[52] US. Cl. ..96/50, 96/61, 96/95, 96/109 [51] Int. Cl ..G03c 5/26, G03c 1/06, G03c 1/34 [58] Field of Search ..96/61, 109, 95,52, 50

[56] References Cited I UNITED STATES PATENTS Chilton et al ..96/50 2,514,650 7/1950 Knott et a1 ..96/52 3,212,892 10/1965 von Konig et a1. .....96/66 3,362,826 l/1968 Weyde et al ...96/l09 3,438,777 4/1969 Willems et al ..96/52 3,239,340 3/1966 Nasu et al ..96/6l FOREIGN PATENTS OR APPLICATIONS 959,182 5/1964 Great Britain ..96/66 1,514,667 2/1968 France ..96/52 Primary Examiner-J. Travis Brown Assistant ExaminerMary F. Kelley Attorney-Connolly and Hutz [57] ABSTRACT Exposed and developed pnotographic silver images can be stabilized by treating the layer containing the exposed image with a compound which reacts with the silver halide in the unexposed and undeveloped areas of the layer to form a light-insensitive reaction product. Fading of the silver images thus produced is prevented by performing the development in the presence of mercapto substituted heterocyclic compounds.

3 Claims, No Drawings STABILISING DEVELOPED PHOTOGRAiI-IIC IMAGES The invention relates to a process for the production L of photographic images by exposure, development and subsequent stabilization, in which the development is carried out in the presence of heterocyclic mercapto compounds in order to improve the stability of the silver image even on prolonged storage under extreme climatic conditions.

It is known to stabilize developed photographic images with complex forming compounds in rapid photographic reproduction processes as a substitute for conventional fixing with sodium thiosulfate followed by washing. In contrast to the method of fixing with sodium thiosulfate, in these stabilizing processes the silver salts remain in the unexposed and undeveloped parts of the layer in the form of a light-insensitive reaction product of the stabilizing compound with the original silver halides. Stabilization of developed photographic materials has, however, certain disadvantages. One disadvantage is that nearly all substances which form complexes with silver halides attack metallic silver and hence the photographic image, converting the silver into a complex compound or simple silver salt. This leads to fading of the silver image or to a change in the color of the image silver from black to a brownish tone. This undesired efiect occurs particularly in a moist atmosphere.

Fading of the black image area can be prevented by adding to the stabilizing bath heterocyclic mercapto compounds such as 1-phenyl-5-mercaptotetrazole. However, the usual compounds of this type are only sparingly soluble in the acid stabilizer solutions so that it is difficult to apply a sufficient quantity of these compounds. They cannot be added in the required quantity to the emulsions because of their development inhibiting effect.

Fading of the black image areas can also be prevented by adding to the emulsion compounds which only decompose in alkaline solution to yield a mercapto compound. Such compounds, however, cannot be added to the emulsion in sufficient quantities to improve satisfactorily the keeping quality of the stabilized image on prolonged storage under extremeclimatic conditions.

It is among the objects of the present invention to provide compounds which do not show the disadvantages referred to above, and which are stabilizing black silver images particularly upon prolonged storage under extreme climatic conditions.

We now have found a process for the production of photographic images including the steps of exposing a supported silver halide emulsion layer, developing and stabilizing the exposed and developed layer wherein development is carried out with a bath which contains at least one heterocyclic compound of the following formulas:

R N N u. S H

H s Y s E f 1| I! l N-N -N wherein represents:

R mercapto,

R amino or substituted amino;

R and R together may represent the ring members required to to complete a Z-mercaptothiadiazole ring;

X -0, S- or R (l) hydrogen, (2) alkyl having up to eight carbon atoms, preferably having one to three carbon atoms, (3) aryl, preferably a ring of the phenyl or naphthyl series; (4) aralkyl such as benzyl or phenyl ethyl; (5) cycloalkyl such as cyclohexyl and (6) amino; these radicals, in particular phenyl rings, may be further substituted, e.g. with halogen such as chlorine or bromine; alkyl or alkoxy groups having preferably up to 5 carbon atoms or hydroxyl groups;

Y (l) alkylene having up to 10 methylene groups, in particular having 2 to 8 methylene groups; (2) cycloalkylene such as cyclohexylene; (3) arylene, in particular a phenylene or naphthylene ring; or (4) aralkylene, e.g. xylylene; Y may be attached to the heterocyclic ring either directly or through oxygen, sulfur or imino groups; furthermore, Y may represent an alkylene chain having three to 10 methylene groups which are interrupted by hetero atoms or groups such as oxygen, sulfur or imino groups.

Particular utility is exhibited by the following compounds:

TABLE 1 Melting No. X Y Point 1 5 (C11,), 287C 2 S (C11,), 2 l 1C 3 S C11,). 198C 4 0 (CH2): 227C 5 0 (CH,). 191C 6 0 (C11,). 143C 7 0 (CH,)., 106C 8 S S-CH,-S 174C 9 S S-(CHsh-S 214C 10 S S-(CH,),--S 162C 1 l S S(CH,),-S 191C 12 S S(CH,).S 162C 13 S S(CH,),S 146C 19 S Q 299C The preparation of compounds 1 to 3 has been described in Chemisches Zentralblatt (1958), page 13755. Compounds 4 to 7 are prepared by condensation of carbodisulfide with the corresponding dicarboxylic acid dihydrazides as described in J. Amer. Chem. Soc. 78, 4475 (1956). The preparation of compounds 8 to have been described in German Pat. specification No. 1,217,784 corresponding to U.S. Pat. No. 3,223,524, that of compounds 16 to 20 in German Patent specification No. 1,175,077 corresponding to U.S. Pat. No. 3,212,892.

The preparation of these compounds has been described in U.S. Pat. application Ser. No. 809,415.

HS //N\N H N N- HSH m.p. 197 C.

s N fisljf f N-||-SH |n.p. 195 C.

Emulsions which have a high silver chloride content are preferred.

The binders for the light-sensitive layers may be the usual water-permeable layer-forming substances, particularly proteins, preferably gelatine.

Furthermore, the emulsions may contain alkylene oxide polymerization products as chemical sensitizers. They may also contain the known stabilizers.

In addition, the emulsions may contain developers or developer combinations of the type hydroquinone, pyrocatechol, aminophenol, compounds of the pyrazolidone series, phenylene diamine derivatives and the like, antioxidants for the developer, e.g. potassium metabisulfite, aldehyde and ketone bisulfite, matting agents and brightening agents.

Development is carried out in the usual manner, using known developers. According to a preferred method of carrying out the invention, the developer is added to the photographic material and development is initiated by treatment with an alkaline aqueous bath, hereinafter referred to as an activator bath.

The concentration of the compounds for use according to the invention in the development bath may vary within wide limits. The concentration depends upon the photographic material used and the nature of the developer. The optimum concentrations for a particular reproduction process can be determined by a few simple laboratory tests. Amounts of 0.5 to 10 g per liter of treatment bath, preferably 1 to 5 g per liter, have generally been found to be sufficient.

Suitable stabilizing agents, i.e. compounds which are capable of converting the silver halide remaining after development into a compound which is not sensitive to light, have been described e.g. in British Pat. Nos. 631,184 or 959,807 and in U.S. Pat. No. 2,525,532 or French Pat. No. 1,237,454. Ammonium thiocyanate and alkali metal thiocyanates, e.g. sodium or potassium thiocyanate, have been found to be particularly suitable.

These stabilizing baths may also contain the usual other additives such as alkali metal sulfites or metabisulfites or cycloalkanone bisulfites, acetic acid or its salts and organic compounds, particularly additional heterocyclic compounds which contain mercapto groups, such as 1-phenyl-5-mercaptotetrazole, which form sparingly soluble silver salts.

Example 1 A light-sensitive photographic material comprising a supported silver chloride gelatin emulsion layer which emulsion layer contains 0.2 mol of silver halide with a silver iodide content of less than 0.1 mol of silver iodide per kg of emulsion (amount of silver in the form of silver halide 1.3 g/m) and hydroquinone (12 g of hydroquinone per kg of emulsion) is exposed to form an image and developed in the following activator solution:

60 g of sodium hydroxide 50 g of anhydrous sodium sulfite 2 g of potassium bromide made up to 1 liter with water.

The compounds listed in Table 3 below are added to the above activator solution. The quantities added are shown in the table.

The developed material is then treated with the following stabilizing solution:

250 g of ammonium thiocyanate 145 g of potassium metabisulfite 100 ml of a 3% aqueous solution of formaldehyde 25 ml of 60% acetic acid, made up to 1 liter with water.

The samples are processed in a two-bath development apparatus customarily employed. The treatment time is about 1 to 5 seconds in the activator bath and about 2 to seconds in the stabilizing bath.

To test the stability in storage of the silver image, a portion of the copy is kept over water in a vessel for 24 hours.

Several of these uniformly moist portions of the copy are inserted into a polyethylene container and this container is placed in a bag containing 30 ml of water and sealed. The sealed containers are stored in a heating cupboard at 60C for 5, 24 and 48 hours, respectively, and the change of the silver image which has taken place after this time is examined.

Whereas the silver image of the copies produced according to the invention remains black or dark brown to black depending on the time of storage, under the above condition the comparison sample shows discoloration varying from brown to pale brown. The maximum density of the various fresh, air-dried materials and those which have been stored in moist heat is measured in a densitometer. The following results are obtained:

TABLE 3 Maximum density The photographic material described in Example 1 is exposed to form an image and developed in the following activator solution:

50 g of sodium hydroxide,

40 g of anhydrous sodium sulfite,

2 g of potassium bromide,

1 g of 1-phenylpyrazolidone-(3), made up to 1 liter with water.

The compounds indicated in Table 4 below are added to the above activator solution. The quantities added are shown in the table.

The developed material is treated with the following stabilizer solution:

250 g of ammonium thiocyanate,

80 g of potassium metabisulfite,

ml of 60 percent aqueous acetic acid,

20 g of cyclohexanone-sodium bisulfite addition compound, made up to 1 liter with water.

Processing is then continued as described in Example 1.

Most of the compounds mentioned in the two examples also improve the stability of the white image portion, i.e. they prevent yellowing of copies stored in a moist and warm atmosphere.

Example 3 A light-sensitive photographic material comprising a supported silver bromide gelatin emulsion layer containing 0.26 mol of silver halide including 0.8 mol of silver iodide per kg of emulsion (amount of silver in the form of silver halide 2.5 g/m) and hydroquinone per kg of emulsion) is exposed to form an image and then treated as described in Example 1.

The compounds indicated in Table 5 below are added to the activator solution. The quantities added are shown in the table.

TABLE 5 Maximum density Additive concen- Compound tration Airafter moist warm storage for No. gll Dried 5 hours 24 hours 48 hours Control sample 1.92 1.41 1.08 0.60 11 Z 1.88 1.81 1.70 1.51 27 2 1.93 1.88 1.68 1.48 37 2 1.94 1.94 1.80 1.60 39 2 1.92 1.93 1.81 1.63

We claim:

the image -preserving substance in the amount ofO.5 to R hydrogen atom; an alkyl group having up to 10 grams per liter in the alkaline aqueous bath consisteight carbon atoms; an aryl group; an aralkyl ing essentially of at least one heterocyclic compound of group; a cycloalkyl group or an amino group; the following formulas Y an alkylene group having up to 10 methylene groups, cycloalkylene, arylene or aralkylene, Y I 1 being attached to the heterocyclic ring either I directly or via oxygen, sulfur or imino groups, R2N -SH furthermore, Y may represent an alkylene chain H X X having three to methylene groups which are in- HS Y SH 10 terrupted by hetero atoms such as oxygen, sulfur J fly I or imino groups.

2. The process of claim 1, wherein the stabilizing h i bath in addition contains cyclohexanone bisulfite. R i a mercapto group; 3. The process of claim 1, wherein X represents R is an amino group or R taken together with R represents the ring members required to complete a 2-mercaptothiadiazole /N R3 ring; X S or and Y alkylene having three to 10 methylene which are \N R3' interrupted by oxygen or sulfur. 

2. The process of claim 1, wherein the stabilizing bath in addition contains cyclohexanone bisulfite.
 3. The process of claim 1, wherein X represents and Y alkylene having three to 10 methylene which are interrupted by oxygen or sulfur. 